![]() How did you connect the 12V ? Only the power jack (DC power barrel jack) or the VIN pin. If you wan to add reverse polarity protection without the higher voltage drop of either a PN diode like the M7 diode (~0.7V) or a good schottky (~0.5V), you can always play the trick of using a backwards connected P-channel mosfet.I didn't check the schematic or the board layout, but that might be a mosfet that is used to turn the USB power off, when power is applied to the power jack. Removing T1 was a simple fix that will keep my PC safe when back feeding 5V. I was going to do this by changing one of the 10k resistors to a different value, but this was impractical since they are arrays and you can't change only one resistor. ![]() I also considered changing the threshold of the comparator so it would turn off the MOSFET when 5V was applied and it back feeds to Vin. I first tried removing the polyfuse, but this prevented the USB from connecting since the USBVCC is used by the USB microcontroller so that did not work. The MOSFET is a SOT-23 packaged part, so it is pretty easy to remove. I marked my board as modified and then taped the MOSFET to the board so I can reinstall it later if I want to. The only downside to this is that I need to have my external 5V power supply on in order to program the Arduino with the PC. I am doing a project that uses a high powered servo, and I want to run the Arduino Uno and the servo off of the same 5V power supply but I still want to be able to safely connect my PC to the USB port without risk of back feeding my computer with 5V from the Arduino.Īfter looking at the schematic for the Arduino, I simply removed used a hot air pen to remove the MOSFET T1 on the Arduino Uno which allows USB power to feed the +5V net. External supply at 5v pin - Installation & Troubleshooting - Arduino Forum A member of the team discussed it with us. The earlier posts discussed bricked boards after putting 5V into the board via the header pin. The 1117 5V regulator is susceptibe to damage when reverse driven. ![]() A 3.3 volt supply generated by the on-board FTDI chip. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.ģV3. The regulated power supply used to power the microcontroller and other components on the board. You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.ĥV. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). I am guessing that I CAN power with my power supply though the 5VDC pin, if I connect a diode between Vin and 5VDC, cathode to Vin. I have customized the supply header to only provide 5VDC and are using it to power several other boards From the description on the product page, it seems possibly, but searching the forum results state that you shouldn't do this? Which is right? How do I power the Arduino Mega Rev 3 from a regulated 5VDC power source (a PC power supply). Sorry for necro'ing this thread, but I have the same question. (I'm trying not to blow up my arduino mega) The next question I have is, if I'm powering the arduino through 5V and then want to program it through the USB can I keep the 5V pin connected and let the arduino choose the power source or must I always disconnect it before connecting the USB cable? Is it just because you could get the polarity and voltage wrong and wreck your arduino or is there something else to be concerned about? If it's the later, should I create a USB B cable with 5V coming from my power supply? I'm a bit concerned that it's not advisable to supply power to the 5V pin. Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). I read that:ĥV.This pin outputs a regulated 5V from the regulator on the board. I've got a 10A V5 power supply that's primarily there to power a bunch of LEDs but I wanted to also use it to power an arduino mega 2560. Firstly, apologies for these basic questions.
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